Telephone-exchange system.



H. W. ULRICH.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 12. I9I7.

Patented Mar. 4,1919.

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E i W STATES ATENT orric HORACE W. ULRICH, EAST ORANGE, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORKgN. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

tablished connections between telephone lines. i

In accordance with this invention each connecting circuit for joining together telephonelines is provided with means whereby when a listening key thereof is actuated an operators telephone set is connected to one end ,of the connecting circuit and a relay is simultaneously energizedto sever the continuity of the connecting circuit. The listening keys of the connecting circuits are also provided with contacts and circuit connections by means of Which,when two keys of different connecting circuits are simultaneously actuated, an energizing circuit fora common relay is established, thereby preventing the connection of the operators telephone set toeither of the connecting circuits with which the actuated listening keys are associated.

A more complete'understanding of this invention may be had from the. following description, considered in connection with the accompan ing drawing illustrating one embodiment t ereof. I

In the drawing there is shown a telephone line A extending from a subscribers station to a central oiiice and there suitably joined with a circuit 0, shown between the lines 11 and 2-2. This circuit C is suitably connected in any desired manner with a circuit extending to a private branch exchange and there joined with a-connecting circuit D, shown between the lines 33 and 4-4. The other end of the connecting circuit D is suitably joined with a telephone line B, extending from the private branch exchange to a station local thereto. Two listening keys 5 and 6 are associated with the connecting circuit D. These listening keys may be controlled by a common plunger (not shown) which, when moved in one direction,

Specification of Letters Patent.

' Patented Mar. 4, 1919.

Application filed July 12, 191'7.- Serial No. 180,133.

opens the normally closed contacts and closes theinormally opened contacts of one listening key, and, when moved in the opposite direction, opens the normal and closes the alternate contacts of the other key. Between the lines 77 and 88 there are shown portions of two listening keys 15 and 16 associated with a connecting circuit similar to D, and to the left of line 88 there are shown portions of two listening keys 25 and 26 associated with a third connecting circuit, similar to D. The listening keys of each of the connecting circuits are exactly alike, but for convenience, only the listening keys of connecting circuit D are shown in full. A relay 9, common to the connectingcircuits at the private branch exchange, has normally closed contacts in circuit with an operators telephone set. It will be understood, of course, that a plurality of lines similar to line B terminate at the private branch exchange and that a plurality of lines similar to line A may be extended to the private branch exchange. Furthermore, that the connecting circuits at the private branch exchange may be employed to interconnect lines local thereto, as well as a line local thereto and a line extended thereto over suitable circuits.

Assuming that subscribers A and B are in communication and that the operator desires tocommunicate with subscriber B, the listening key 6 is actuated. The actuation of this listening key causes the operation of relay 10, individual to the connecting circuit D, over a circuit from battery through the winding of relay 10, conductor 11 and contact 12 of listening key 6 to ground. The operation of relay 10 opens its normally closed contacts, thereby interrupting the continuity of the connecting circuit D and connecting a source of current 13 to the right-hand end of the connecting circuit D through retardation coils 14 and the alternate contact of relay 10. This battery is connected to this end of the cord circuit to furnish current for operating the transmitters of the operators telephone set and the local set B. The actuation of listening key, 6 also connects the operators telephone set to the right-hand end of the connecting circuit D through the normally closed contacts of relay 9, conductors 17 and 18, contacts 19 and 20 of the listening key 6 and conductors 21 and 22.

contacts to interrupt the continuity of the connecting circuit, as hereinbefore described. The operator s telephone set 1s now connectedrwith the left-hand endof the connecting circuit D, through the normallyclosed .con-

tacts of relay 9, conductors 17 and 18-,'c0nductors 27 and 28, contacts 29 and 30 of listening key 5 and conductors 31 and 32.

- Should the connecting circuit with which listening keys 15 and 16 are associated be connected with a'telephone line atthe same time that the connecting circuit D is joined to telephone line B, and should the operator attempt to connect these two lines together by actuating a listening key of each of these connecting circuits, and thereby attempt to listen to the conversation, relay 9 will be:

energized to prevent the connection of the operators telephone set to either of the connecting circuits. For example, assuming that the listening keys 6 and 16 are actuated, theyrclay 9 will then be operated over a circuit from battery through the windingof relay 9, contact 35 of listening key 6, common conductor 36 (which is multipled to normally open contacts of each of the listening keys), contact 37 of listening key 16, portion 38 of a common circuit lead extending in series through normally closed contacts of all the listening keys, contact 39 of listening key 5, portion 10 of the common series circuit. lead and contact 41 of listening key 6 to ground;

F rom the above descriptiomit will be evident that an operator is prevented from listening in on a conversation between two telephone lines joined together by a single connecting circuit and that it is also impos sible for the operator to connect two lines together through portions of two connecting circuits and they operators telephone set. By the provision of a common circuit lead multipledto normally open contacts of the several listening keys and a common circuit lead'extendin'g in series through "normally closed contacts of the several listening keys, the common relay 9 will be energized when any two listening keys of different connecting circuits are simultaneously actuated.

What is claimed is:

1.- A telephone exchange system comprising two telephone lines, a connecting circuit joining the telephone lines together, an operator controlled switch, a relay energized upon the actuation of the switch to interrupt the connecting circuit, and an operato s telephone set connected with one end of the connecting circuit by the actuation of the switch. e i I 2. A telephone exchange system compris ing twotelephone lines, a'connecting circuit joining the telephone lines together, a source of current, an operator controlled switch, a

relay energized upon the actuation of the switch to interrupt the connecting circuit and to connect the source of current to one end thereof, and an operators telephone set connected, by the actuationof the switch,

to prevent the connection of the operators telephone set to the connecting circuits,-and an energizing circuit for the relay estab* lished upon the simultaneous actuation of two keys and including contacts of both keys connected in series;

4. A telephone exchange 'system comprisr ing. telephone lines, connecting circi'iits for interconnecting the lines, a listening key for each connecting circuit actuated to connect the operatofls telephone set thereto, a relay common to the connecting circuits adapted when energized to prevent the connection of the operators telephone set to the co mecting circuits, a circuit lead common to and connected to normally 'opencontacts of the-listening keys, a circuit lead common to and including normally closed contacts of the;

liste11ingkeys,;and an energizing circuit for the relay. established by the simultaneous actuationjof two keys and including. portions of both circuit leads and contacts of both actuated keys.

5'. A telephone exchange system co mpris mg telephone lines, connectingcircuits .for interconnecting the llnes, a listemng key for each connecting circuit actuated to connect the operators telephone set thereto,-a relay.

common tothe connecting circuits adapted when energized to prevent the connection of the operators'telephone setto the connect ingpcircuits, a circuit lead common to and multipled to normally open contacts of the listeningkeys, a circuit lead having contacts of the listening keys included in series therein and in series with one another, and an energizingcircuit for the relay established by V the simultaneous actuation of two .keys and" including portions of bothrcircuitvleads and contactsof both actuated keys.

6. A telephone exchange system comprising telephone lines ,connecting circuitsfor interconnecting the lines, an operators telephone set, a listening. key for each connecting circuit adapted when'actuated to connect the operators telephone set thereto, an keys and including the winding of the relay electromagnetic relay common to the conand a contact of one and two contacts of the necting circuits adapted when energized to other key, the contacts being connected in 10 prevent the connection of the operators teleseries.

5 phone set to the connecting circuits, and an In witness whereof, I hereunto subscribe energizing circuit for the relay established my name this 10th day of July, A. D. 1917. upon the simultaneous actuation of the two HORACE W. ULRICH.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

- Washington, D. (2." 

